1. Field of the Invention
The present invention relates to an information display panel, wherein display media consisting of at least one kind of particle and having optical reflectance and charging characteristics are sealed between two opposed substrates, at least one of which is transparent, and wherein the display media, to which an electrostatic field is applied, are made to move so as to display information such as an image or the like, and also relates to a mother panel to obtain the information display panel.
2. Description of Related Art
As an information display device substitutable for liquid crystal display (LCD), information display device with the use of technology such as an electrophoresis method, an electro-chromic method, a thermal method, dichroic-particles-rotary method have been proposed.
These conventional techniques are considered to be useful for inexpensive visual display devices of the next generation compared with a LCD due to merits such as wider field of vision close to normal printed matter, smaller power consumption or a memory function and expected to be spread out to information displays for portable devices, electronic paper and the like. Recently, electrophoresis method for microencapsulating dispersion liquid made up with dispersion particles and solution and disposing the liquid between opposed substrates, is proposed and expected.
However, in the electrophoresis method, there is a problem that a response rate is slow by the reason of viscosity resistance because the particles migrate among the electrophoresis solution. Further, there is a problem of lacking image writing repetition stability, because particle with high specific gravity and it is difficult to maintain a stability of dispersion state. Even in the case of microencapsulating, the cell size is diminished to a microcapsule level in order to make it hard to show the above-mentioned drawbacks, however, and essential problem is not overcome at all.
Besides the electrophoresis method using behavior in the solution, recently, a method that electro-conductive particles and a charge transport layer are installed in a part of the substrate without using solution has been proposed. [The Imaging Society of Japan “Japan Hardcopy ‘99’ (Jul. 21-23, 1999) Transaction Pages 249-252”] However, the structure becomes complicated because the charge transport layer and further a charge generation layer are to be arranged. In addition, it is difficult to constantly charge the electro-conductive particles, and thus there is a drawback on the lack of display stability.
As one method for overcoming the various problems mentioned above, an information display panel is known, wherein display media consisting of at least one kind of particle and having optical reflectance and charging characteristics are sealed in a cell made by two opposed substrates, and wherein the display media, to which an electrostatic field is applied, are made to move so as to display information such as an image or the like.
In the above-mentioned information display panel, there is a sealing agent placement part in an outer edge portion of a substrate to seal a gap between two substrates by a sealing agent. The display side substrate is pressed by a ram head of a pressing machine and the two substrates are jointed with each other. A member for securing the gap space (rib) is formed on at least either the outer peripheral side or the inner peripheral side of the sealing agent placement part to prevent the display side substrate from bent when a ram head of a pressing machine presses the substrate used as the display side substrate such as one made from resin, which is easy to be bent, to joint two substrates. (Refer to, for example, WO2006/062155)
A method of forming a sealing agent 54 arranged in a sealing agent placement part is known, as shown in FIG. 19 as an example, that an opening portion 55 is provided at a part of the sealing agent 54 arranged in the sealing agent placement part in order to prevent puncture of the sealing agent when the substrate 51 and the opposed substrate are pressed to be attached and to allow gas to escape.
As a typical method used in the sealing agent placement process, a dispense method and a screen printing method are known. The dispense method is a method of applying and arranging a sealing agent discharging from a dispenser on a substrate and it is necessary to make the sealing agent unicursal for each pattern. The screen printing method is a method of copying and arranging the sealing agent on a necessary area with a mask. The dispense method is also used for applying the sealing agent to seal an opening provided in a part of the sealing agent arranged.
In FIG. 20 there is shown an example of other conventional example of an opening portion 55 provided in the sealing agent 54 arranged in the sealing agent placement part.
FIG. 20a is a mother substrate sheet for producing an information display panel. This mother substrate sheet is a substrate before attached, in which a sealing agent is arranged in a sealing agent placement part on at least one area corresponding to each information display panel.
Two mother substrate sheets attached with each other, which are not divided into each information display panel yet, are called a mother panel. FIG. 20b is an enlarged view of the opening portion of the information display panel surrounded with a circle shown in FIG. 20a. In FIG. 20b, a dashed line indicates a section line of the mother panel. The left side of the dashed line indicates an information display panel part having display area 53 while the right side indicates a non information display panel part. The mother panel is cut along the dashed line to obtain an information display panel.
A first problem of the above-mentioned conventional information display panel will be described. The amount of the sealing agent arranged in a seal corner part is more than that in other areas so that deformation such as corner break and the like generated in the substrate press process easily occurs at the seal corner part. When the amount of deformation is especially large and when the sealing part and the member for securing the gap are contacted, there are risks that a hole is generated in a part of the sealing part or sealing property is degraded because the line width of the sealing part locally becomes thin.
As a second problem, in the producing method disclosed in the above-mentioned [The Imaging Society of Japan “Japan Hardcopy ‘99’ (Jul. 21-23, 1999) Transaction Pages 249-252”], the opening portion 55 provided in the sealing agent 54 arranged in the sealing agent placement part is used only for degasification when the substrate 51 is attached to the other substrate by pressing and there is no description about the handling after the information display panel is produced. It is considered that the opening portion 55 should be sealed in order to ensure the panel reliability, however, a producing method of sealing the opening portion 55 in an appropriate state has not been found.
As a third problem, in FIG. 20b the placement start portion 54S of the sealing agent after the sealing agent is arranged is likely to be larger than the design value when the dispense method is used. That is because a dispenser is likely to cause dripping just after starting discharge.
The opening portion 55 is provided at a part of the sealing agent of the sealing agent placement part and sealed after two substrates are attached. In order to ensure the sealing, the opening portion 55 with an excessively narrow width is provided. Therefore, due to dripping or seal crack in pressing the substrates, the opening portion 55 is easily sealed, which means that there is no escape of gas generated when the sealing agent is cured and results in problems such as seal puncture and the like.
When the screen printing method is used, at the end portions such as the placement start portion 54S and placement last portion 54E of the sealing agent after the sealing agent is arranged shown in FIG. 20b, the amount of copy of the sealing agent is larger so that the opening is likely to be sealed as is the case using the dispense method.